Reactive vaccination as an effective tool for measles outbreak control in measles mortality reduction settings, Democratic Republic of Congo, 2005-2006.

New WHO guidelines for measles outbreak response in measles mortality reduction settings now include reactive vaccination for outbreaks. Here we used surveillance data and vaccine coverage surveys following two mass vaccine campaigns in the Democratic Republic of Congo, to show the impact of reactive vaccination on reducing cases during outbreaks. The number of measles cases reported was collected via the national surveillance system. Following vaccination campaigns, two-stage cluster sampling surveys were used to evaluate pre and post campaign coverage. In Matadi, 1035 cases were reported from 24 October 2005 to 19 February 2006 and in Mbuji Mayi, 4734 cases were reported from 3 October 2005 to 30 April 2006. Following the mass vaccination campaign, coverage rose from 87.5% (95% CI 87.2-87.8) to 97.1% (95% CI 96.9-97.3) in Matadi and from 74.0% (95% CI 70.9-77.0) to 96.5% (95% CI: 95.7-97.2) in Mbuji Mayi. Weekly reported cases reduced respectively by 89.3% and 68.9% in the 3 weeks following the mass vaccination campaigns. The introduction of reactive vaccination for measles outbreak control provides an additional tool to help reduce the impact of outbreaks. Our experience shows that this type of intervention is feasible and effective even when baseline vaccination coverage is > 70%.